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New tanks

Molloy Precast

Introducing our new range of precast concrete pump sumps: they range in depths from 3m to 6m. They are part of our new range of larger tanks.

Percolation installation and sizing

Molloy Precast

How does a percolation area work?

A percolation system is now standard for all new septic tanks installed in Ireland today. These systems are engineered to treat the partially treated effluent from the septic tank and to distribute this treated liquid into the underlying ground water. If constructed correctly, and the site has the right conditions a standard percolation system will last trouble free for many years with little maintenance. A typical percolation system is composed of a series of trenches half a meter wide and 18m long. Each trench is made up of the following components as seen in the image below, 250mm of clean stone, a 4” distribution pipe, a second layer of clean stone to cover the pipe and a geotextile membrane covered with a layer of soil brought up to ground level. It is important that the trench is ventilated for an adequate oxygen supply. This is achieved by connecting the pipes at the end of each trench together and pointing a single pipe out of the ground for ventilation. This ventilation pipe can be brought up near a fence or boundary if desired. Effluent from the septic tank has to be fed into a distribution box. The purpose of this box is to ensure that each trench receives an equal volume of wastewater. Over dosing one trench will cause that trench to breakdown.

Biological treatment of the wastewater is achieved at the soil/stone interface, where a layer of bacteria or biofilm uses pollutants in the wastewater as a food source under oxygen rich conditions. This process ensures a pollutant free liquid enters the ground water system. To ensure that effluent is adequately treated a depth of 900 mm of un-saturated soil is required as a buffer between the invert of the trench and the water table.

Common percolation installation errors

Errors are often made when constructing percolation systems, which often lead to failure of the system. It is important that the distribution stone used in the trench is clean as residue on dirty stone can settle on the bottom of the bed creating an impermeable layer causing the percolation area to fail. The distribution pipe used should be perforated and rigid. Traditionally flexible land drainage pipe was used, this pipe has two major flaws and under no circumstances should it be used in a new percolation system. Land drainage pipe is flexible and often creates hills and hollows which will prevent flow along the length of the pipe. In addition, land drainage pipe is ribbed which also restricts flow along the pipe.

Percolation cross section

Sizing a percolation area

The number of trenches required for a domestic house is dictated by the number of people in the household, one trench per person. Most County Councils assume that every bedroom has a potential occupancy of 2 persons. For example a three bedroom household to have a potential of 6 occupants and hence 6 trenches are required.

Percolation trenches

Domestic Wastewater Treatment

Molloy Precast

Over 400,000 households in Ireland have on-site wastewater treatment systems. Typical wastewater treatment systems have two components, namely, a septic tank and a percolation area. Both components are essential to ensure adequate wastewater treatment. Inadequately treated wastewater can impact on the quality of ground water, drinking water and surface water which in turn can affect human health as well as the surrounding environment.

Domestic wastewater is made up of solids, biological pollutants as well as fats, oils and greases (FOGs). Removal of these materials is by a combined effort between the septic tank and percolation system. The purpose of a septic tank is to remove FOGs and solids from the wastewater, while the purpose of the percolation area is to biologically treat the wastewater, removing biological pollutants and to distribute treated wastewater into the groundwater network. It is vital that both components are installed and maintained properly to ensure a trouble free on-site wastewater treatment system.

Other more advanced types of wastewater treatment systems include secondary treatment systems with polishing filters, septic tanks with bio-filters, septic tanks with reed beds and percolation systems and willow beds. These more advanced types of systems are required on poor sites. A site with good/reasonable soakage is suitable for a basic on-site wastewater treatment system. There are several site complications which might necessitate an advanced wastewater treatment system such as:

  • High water-table or high bedrock
  • Poor soakage
  • Small site
  • Sensitive area

Current legislation and guidelines

The current guidelines for the installation of on-site wastewater treatment systems in Ireland are contained within the EPA “Code of practice for wastewater treatment systems for single houses”, 2009. Septic tanks installed in Ireland should be certified to meet EN 12566-1 standards. Secondary treatment systems installed in Ireland should be certified to meet EN 12566-6 standards. Proposed new regulations dealing with domestic wastewater treatment systems were published earlier this year and some of the conditions include:

  • Homeowners should be aware of the location of their on-site wastewater treatment system and should carry out an annual visual inspection, to determine if it is causing pollution or is in need of maintenance
  • Only domestic wastewater should enter the treatment system, i.e. “black water (wastewater from toilets) and grey water” (Wastewater from showers, sink, kitchen etc.). - - Rainwater derived from roofs or surface water Should be excluded from the system. The homeowner must ensure that discharge from the treatment system only goes into the ground and does not seep, leak or otherwise escape from any part of the system where it is not intended to.
  • The homeowner must ensure that discharge is not to the surface of the ground and that wastewater does not rise to the surface causing “ponding”.
  • The homeowner must ensure that discharge is not directly into surface waters such as streams or rivers unless licenced to do so.
  • Sludge removal is dependent on occupancy and size of the septic tank. Larger tanks reduce de-sludging frequency. It is the homeowner’s responsibility to annually check the depth of sludge in their tank, if sludge depth is one third the height of the total liquid depth de-sludging is recommended. Only permitted wastewater collectors are allowed collect and transport sludge, this is to ensure it is disposed of in accordance with legislation.
  • The tank capacity and configuration should be large enough to create a big enough dwell time to allow a septic tank function properly - Roof water and surface water are not allowed to enter the wastewater treatment system
  • Inlet and outlet pipework must be free of blockages
  • Manhole covers, tanks, pipeworks, distribution boxes and t-pieces must be in good working order
  • Any distribution box must ensure even distribution between all trench
  • Any mechanical or electrical equipment must be fit for purpose and operational
  • Aeration vents should be dry and free from obstructions
  • Operational and maintenance regimes, as set out by the manufacturer, must be complied with.

Septic Tank Problems

Molloy Precast

If you are having difficulties with your Septic Tank, the decision tree below helps find the issue with your septic tank, and points you towards possible solutions.

Septic tank problem

Troubleshooting problems with the on-site wastewater treatment system

Problems with septic tanks are generally noticed when toilets and other household utilities stop functioning properly or if the septic tank begins to overflow. The first thing to check when this happens is if the pipes leading to the septic tank are blocked. If the water levels in the septic tank are normal, then there is a blocked or collapsed pipe somewhere. If this is not the case there is either something wrong with the septic tank or the percolation system. Listed below are some common problems and some solutions, it is recommended that where a complicated problem is encountered the homeowner consult with a competent person/company.

If the problem only occurs occasionally:

Check if there is rainwater entering the system. To do this, in dry weather pour water into the rainwater pipe system (gutters/manholes), check if it enters the septic tank. Solution – A Check for surface water entering the system via tank lids or manholes during wet conditions. Solution – B If there is no surface water or rainwater entering the system, it is likely that the percolation system is starting to break-down, consider replacing it with a new one.

If the problem is consistently occurring all year round:

Investigate the type of percolation system, if it is a soak pit, it is likely that this has failed and may need to be replaced. Soak pits are not long term solutions for wastewater disposal. Traditionally these were used to distribute the effluent from a septic tank into the ground. More often than not these soak pits give trouble; there are several reasons why this might happen, some of the more common reasons are: A soak pit is not designed to treat wastewater, it does not have enough surface area for an adequate amount of biofilm to grow, or have a ventilated oxygen source to ensure appropriate treatment of the wastewater. This can cause a build-up of substances which will reduce and eventually stop soakage into the ground, causing the septic tank to back-up. This is generally the problem if a soak-pit fails after a number of years of good operation. Solution – C Often times the land taking the effluent does not have good soakage properties, causing the soak pit to fill and hence the tank to back-up, generally this is noticed straight after the system is installed, however, this problem can combine with the previous problem and cause trouble after a few years of operation. Depending on soakage properties two separate solutions can be applied. If the land has good soakage solution C could be employed, however, if the land has poor soakage solution D might be required. The underground water table could be high enough to render the soak pit useless, i.e. the tank can never empty as it is flooded with ground water. In these cases the groundwater is directly polluted by raw wastewater. This might only be a seasonal problem, i.e. long periods of wet weather. Solution E

If the wastewater is pumped from a secondary treatment system or septic tank, check if the pumps are working properly, or if the power supply is working. Solution – F Some problems with on-site wastewater treatment systems which might arise do not directly impact on the functionality of household utilities. These problems can be associated with the septic tank or the percolation system. These issues often cause pollution unknowingly to the homeowner.

Site Assessors in Ireland

Molloy Precast

Home Builders: Molloy Precast can provide you with a Site Suitability Report; however, this report is based on a site characterisation report completed by a competent and qualified person i.e. a site assessor. This page provides you with a list of names and contact details county by county of site assessors.

Site Assessors: To be included in this list, free of charge, please phone John Brennan on 057 93 26000 or email john.brennan@molloyprecast.com.

County Carlow

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Cavan

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Brendan Cooney Building & Environmental Services Engineering Killyvalley, Ballyjamesduff, Co. Cavan brendancooney10@eircom.net (087)9150872
  • Nevin Traynor Traynor Environmental Ltd. Belturbet Business Park, Creeny, Co. Cavan nevin@traynorenvironmental.com (087)7947793 or (049)9522236

County Clare

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Alan McNamara Munster Energy Agency Unit D1, Harbour Village, Killaloe, Co. Clare info@munsterenergyagency.ie 061 622850 or 0877412930
  • Eamon Dunne Dunne Design, Caherush, Quilty, Co. Clare info@dunnedesign.ie or 087 9160 743
  • Annie McEnery Ballyhee, Larchill, Ennis, Co. Clare annie@safi.ie 0874160875
  • Brian Foudy B.Eng. MIEI 1st Floor, Unit 7, Block G,
  • Riverside Business Park, Quin Road, Ennis, Co. Clare brian@foudyconsulting.ie 0871216835 www.foudyconsulting.ie

County Cork

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Donegal

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Dublin

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Galway

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Tom Mackey Mackey Energy & Planning Services 166, Cloch Og, Oranmore, Co. Galway mackey_t@eircom.net or 0863892708
  • Brendan Slevin Brendan Slevin & Associates Bridge St., Gort, Co. Galway brendanslevin@ireland.com (091)630199 or (086)2342657

County Kerry

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Kildare

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Dr. Eugene Bolton Trinity Green, Clonfert, Maynooth, Co. Kildare eugenembolton@gmail.com (086)2434828
  • Aidan Comerford PO Box 1012, Blessington Road, Nass, Co. Kildare aidan@wastewater.ie (086)6042822
  • Darren Daly Ballyhagan, Carbury, Co. Kildare cilldaraengineering@gmail.com (046)9772276 or (087)8193598
  • Declan Kearns Declan Kearns & Associates, Tullywest, Kildare, Co. Kildare info@dkassociates.ie (045)520642 or (086)2111590

County Kilkenny

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Dr. Heather Scully Kilgallen & Parthners Consulting Engineers, 3 Danville Business Park, Kilkenny info@kilgallen.ie (057)8662860

County Laois

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

Desmond Kilmartin Desmond Kilmartin Design Services and Consulting Engineers, Longford, Camross, Portlaoise, Co. Laois kilmartindp@eircom.net or 0868429759

  • Dr. Heather Scully Kylekiproe, Well Road, Portlaoise, Co. Laois info@kilgallen.ie 0578662860
  • Laois County Council carry out all site characterisation reports in the County: Laois County Council Áras an Chontae, Portlaoise, Co. Laois 0578664000

County Leitrim

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Hilary Phelan Drumsna, Co. Leitrim phelanhills@eircom.net

County Limerick

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Janet Costello Co. Limerick janet.costello@gmail.com 0868564658
  • John Slattery Environmental Site Assessment (ESA), Cahir Park, Cahir, Co.Tipperary 087-8244113 or 052-7442775

County Longford

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

Name Address Contact details David Leonard David Leonard Engineering Services, Leitrim, Dring, Co. Longford dleonardeng@yahoo.com 0872444218 Brendan Quaine QA Design No.1 New St. Longford bquaine@eircom.net 0868753615 or 0433348551

County Louth

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Mayo

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Meath

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Cathal Boylan Leitrim, Mullagh, Kells, Co. Meath info@boylancivilengineering.ie
  • Robert Meehan 86 Athlumey Castle, Navan, Co. Meath talamh@ireland.com 0876875558

County Monaghan

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

Name Address Contact details Fergal Coyle FJ Coyle & Associates 3 High St., Monaghan, Co. Monaghan fergal@fjcoyle.ie 0862236096 or 04772175

County Offaly

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Offaly County Council carry out all site characterisation reports in the County: Offaly County Council Áras an Chontae, Charleville Road, Tullamore, Co. Offaly webmaster@offalycoco.ie or 0579346800
  • Dermot Keyes Keyes Consulting, Killina, Tullamore, Co Offaly 086 3131830 or dermot.keyes@keyesconsulting.ie

County Roscommon

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Sligo

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

County Tipperary

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • John Delaney Geoenvironmental, 2 Carraig Duin, Thurles, Co. Tipperary info@geoenvironmental.ie 0877556013
  • Declan Glynn McHugh Glynn and Associates Ltd, Bank Street, Templemore, Co. Tipperary declan@mchughglynn.ie 0504 31142 or 0872362259
  • Michael Murphy Woodbine, Powerstown, Clonmel, Co. Tipperary mlmce@eircom.net 0526184586 or 0877737785
  • John Slattery Environmental Site Assessment (ESA), Cahir Park, Cahir, Co.Tipperary 087-8244113 or 052-7442775

County Waterford

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Joe Moynihan Lackendarra Lodge, Ballinamulty, Via Clonmel, Co. Waterford joe.moynihan@hotmail.com 0876575467

County Westmeath

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • John Brennan Marlinstown Office Park, Marlinstown, Mullingar, Co. Westmeath j.brennan@ors.ie 04493422518 or 0868533043
  • Noel Fay Fay Engineering, Whitepark, Dysart, Mullingar, Co. Westmeath fayengineering@gmail.com 087 2538382
  • James Harkins Hillquater, Coosan, Athlone, Co. Westmeath jamesjharkins@gmail.com 0862397810 or 0906478911
  • Gordon Mitchell Mitchell Murtagh Consulting Engineers, 44 Village Green, Killucan, Co. Westmeath info@mitchellmurtagh.ie 0449358981 or 0868261533
  • Patrick Murphy 1st Floor, 6 Centre Court, Blyry Business Park, Athlone, Co. Westmeath. patrick.murphy@mmarchitecture.ie 0863022438 or 0906460006
  • Ciaran Spollen Annagh, Ballykeeran, Co. Westmeath. 086-8126585 or spollenciaran@gmail.com

County Wexford

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Michael Kehoe Ballingale, Ferns, Eniscorthy, Co. Wexford mkenvsolutions@eircom.net 0863364102
  • Dennis Morrissey Fethard-on-sea, New Ross, Co. Wexford dennis.morrissey@oceanfree.ie 0868843078

County Wicklow

If you are a site assessor in this county and would like to be listed free of charge, please contact us.

  • Margaret Flynn Drumreagh, Donard, Co. Wicklow flynndesign@gmail.com 045404910 or 0879083268